rCitrusBBC: a bacterial resource to mine for new agricultural probiotics for citrus

A culture collection of 147 selected bacteria from the rhizospheric citrus microbiome is available at the Valencian Institute of Agricultural Research (València, Spain). The data include information on plant growth-promoting (PGP) traits published to date and the presence of PGP-related genes in the available genomes of the different bacterial species

Recovery of Pseudomonas savastanoi pv. savastanoi from symptomless shoots of naturally infected olive trees

Seasonal dynamics of Pseudomonas savastanoi pv. savastanoi (Psv) on stems and leaves from symptomless shoots of naturally infected olive trees was monitored in Spanish olive orchards. Data inferred from the comparison between washing of leaves and dilution-plating versus leaf printing of individual leaves suggested that Psv population sizes varied by over several orders of magnitude, among leaves sampled concurrently from the same shoot. We did not find significant differences between leaves and stems, in respect to the number of samples where Psv was isolated or detected by PCR, showing that Psv colonizes both leaves and stems. The frequencies of Psv isolation and average populations were highly variable among field plots. No correlation between Psv populations and those of non-Psv bacteria in any plant material or field plot was observed. However, where both Psv and yellow Pantoea agglomerans colonies were isolated a positive correlation was found. In a selected field plot, dynamics of Psv over three years showed significant differences between summer and the rest of seasons. The highest Psv population occurred in warm, rainy months, while low numbers were generally found in hot and dry months. [Int Microbiol 2007; 10(2):77-84

From the bacterial citrus microbiome to the selection of potentially host-beneficial microbes

Citrus is the most cultivated fruit crop worldwide. The modern citrus industry needs new bioproducts to overcome phytopathological threats, tolerate stresses and increase yield and quality. Mutualistic microbes from roots significantly impact host physiology and health and are a potentially beneficial resource. The bacterial microbiome can be surveyed to select potentially host-beneficial microbes. To achieve this goal, a prevalent “core-citrus” bacterial microbiome was obtained by picking those operational taxonomic units (OTUs) shared among samples within and across two Citrus rootstock genotypes grown in the same soil for more than 20 years. A sub-selection of main OTUs from the defined "core-citrus" microbiome was made based on abundance, host-enriched versus bulk soil, and rhizosphere-indicator species. In parallel, an extensive census of the cultivable microbiota was performed to collect a large number of bacterial citrus isolates. Metataxonomic data were linked to cultured microbes, matching 16S rRNA gene sequences from bacterial isolates with those counterpart OTU reference sequences from the selected bacterial "core-citrus" microbiome. This approach allowed selection of potentially host-beneficial bacteria to mine for agricultural probiotics in future biotechnological applications required for the citrus industry